/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina;

import java.beans.PropertyChangeListener;
import java.io.File;

import javax.management.ObjectName;

import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.juli.logging.Log;


/**
 * A <b>Container</b> is an object that can execute requests received from a client, and return
 * responses based on those requests.  A Container may optionally support a pipeline of Valves that
 * process the request in an order configured at runtime, by implementing the <b>Pipeline</b>
 * interface as well.
 * <p>
 * Containers will exist at several conceptual levels within Catalina.  The following examples
 * represent common cases:
 * <ul>
 * <li><b>Engine</b> - Representation of the entire Catalina servlet engine,
 * most likely containing one or more subcontainers that are either Host or Context implementations,
 * or other custom groups.
 * <li><b>Host</b> - Representation of a virtual host containing a number
 * of Contexts.
 * <li><b>Context</b> - Representation of a single ServletContext, which will
 * typically contain one or more Wrappers for the supported servlets.
 * <li><b>Wrapper</b> - Representation of an individual servlet definition
 * (which may support multiple servlet instances if the servlet itself implements
 * SingleThreadModel).
 * </ul>
 * A given deployment of Catalina need not include Containers at all of the levels described above.
 * For example, an administration application embedded within a network device (such as a router)
 * might only contain a single Context and a few Wrappers, or even a single Wrapper if the
 * application is relatively small.  Therefore, Container implementations need to be designed so
 * that they will operate correctly in the absence of parent Containers in a given deployment.
 * <p>
 * A Container may also be associated with a number of support components that provide functionality
 * which might be shared (by attaching it to a parent Container) or individually customized.  The
 * following support components are currently recognized:
 * <ul>
 * <li><b>Loader</b> - Class loader to use for integrating new Java classes
 * for this Container into the JVM in which Catalina is running.
 * <li><b>Logger</b> - Implementation of the <code>log()</code> method
 * signatures of the <code>ServletContext</code> interface.
 * <li><b>Manager</b> - Manager for the pool of Sessions associated with
 * this Container.
 * <li><b>Realm</b> - Read-only interface to a security domain, for
 * authenticating user identities and their corresponding roles.
 * <li><b>Resources</b> - JNDI directory context enabling access to static
 * resources, enabling custom linkages to existing server components when Catalina is embedded in a
 * larger server.
 * </ul>
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 */
public interface Container extends Lifecycle {

    // ----------------------------------------------------- Manifest Constants


    /**
     * The ContainerEvent event type sent when a child container is added by <code>addChild()</code>.
     */
    public static final String ADD_CHILD_EVENT = "addChild";


    /**
     * The ContainerEvent event type sent when a valve is added by <code>addValve()</code>, if this
     * Container supports pipelines.
     */
    public static final String ADD_VALVE_EVENT = "addValve";


    /**
     * The ContainerEvent event type sent when a child container is removed by
     * <code>removeChild()</code>.
     */
    public static final String REMOVE_CHILD_EVENT = "removeChild";


    /**
     * The ContainerEvent event type sent when a valve is removed by <code>removeValve()</code>, if
     * this Container supports pipelines.
     */
    public static final String REMOVE_VALVE_EVENT = "removeValve";

    // ------------------------------------------------------------- Properties

    /**
     * Obtain the log to which events for this container should be logged.
     *
     * @return The Logger with which this Container is associated.  If there is no associated Logger,
     * return the Logger associated with the parent Container (if any); otherwise return
     * <code>null</code>.
     */
    public Log getLogger();


    /**
     * Return the logger name that the container will use.
     *
     * @return the abbreviated name of this container for logging messages
     */
    public String getLogName();


    /**
     * Obtain the JMX name for this container.
     *
     * @return the JMX name associated with this container.
     */
    public ObjectName getObjectName();


    /**
     * Obtain the JMX domain under which this container will be / has been registered.
     *
     * @return The JMX domain name
     */
    public String getDomain();


    /**
     * Calculate the key properties string to be added to an object's {@link ObjectName} to indicate
     * that it is associated with this container.
     *
     * @return A string suitable for appending to the ObjectName
     */
    public String getMBeanKeyProperties();


    /**
     * Return the Pipeline object that manages the Valves associated with this Container.
     *
     * @return The Pipeline
     */
    public Pipeline getPipeline();


    /**
     * Get the Cluster for this container.
     *
     * @return The Cluster with which this Container is associated. If there is no associated Cluster,
     * return the Cluster associated with our parent Container (if any); otherwise return
     * <code>null</code>.
     */
    public Cluster getCluster();


    /**
     * Set the Cluster with which this Container is associated.
     *
     * @param cluster the Cluster with which this Container is associated.
     */
    public void setCluster(Cluster cluster);


    /**
     * Get the delay between the invocation of the backgroundProcess method on this container and its
     * children. Child containers will not be invoked if their delay value is positive (which would
     * mean they are using their own thread). Setting this to a positive value will cause a thread to
     * be spawned. After waiting the specified amount of time, the thread will invoke the {@link
     * #backgroundProcess()} method on this container and all children with non-positive delay
     * values.
     *
     * @return The delay between the invocation of the backgroundProcess method on this container and
     * its children. A non-positive value indicates that background processing will be managed by the
     * parent.
     */
    public int getBackgroundProcessorDelay();


    /**
     * Set the delay between the invocation of the execute method on this container and its children.
     *
     * @param delay The delay in seconds between the invocation of backgroundProcess methods
     */
    public void setBackgroundProcessorDelay(int delay);


    /**
     * Return a name string (suitable for use by humans) that describes this Container.  Within the
     * set of child containers belonging to a particular parent, Container names must be unique.
     *
     * @return The human readable name of this container.
     */
    public String getName();


    /**
     * Set a name string (suitable for use by humans) that describes this Container.  Within the set
     * of child containers belonging to a particular parent, Container names must be unique.
     *
     * @param name New name of this container
     * @throws IllegalStateException if this Container has already been added to the children of a
     * parent Container (after which the name may not be changed)
     */
    public void setName(String name);


    /**
     * Get the parent container.
     *
     * @return Return the Container for which this Container is a child, if there is one. If there is
     * no defined parent, return
     * <code>null</code>.
     */
    public Container getParent();


    /**
     * Set the parent Container to which this Container is being added as a child.  This Container may
     * refuse to become attached to the specified Container by throwing an exception.
     *
     * @param container Container to which this Container is being added as a child
     * @throws IllegalArgumentException if this Container refuses to become attached to the specified
     * Container
     */
    public void setParent(Container container);


    /**
     * Get the parent class loader.
     *
     * @return the parent class loader for this component. If not set, return {@link
     * #getParent()}.{@link #getParentClassLoader()}. If no parent has been set, return the system
     * class loader.
     */
    public ClassLoader getParentClassLoader();


    /**
     * Set the parent class loader for this component. For {@link Context}s this call is meaningful
     * only <strong>before</strong> a Loader has been configured, and the specified value (if
     * non-null) should be passed as an argument to the class loader constructor.
     *
     * @param parent The new parent class loader
     */
    public void setParentClassLoader(ClassLoader parent);


    /**
     * Obtain the Realm with which this Container is associated.
     *
     * @return The associated Realm; if there is no associated Realm, the Realm associated with the
     * parent Container (if any); otherwise return <code>null</code>.
     */
    public Realm getRealm();


    /**
     * Set the Realm with which this Container is associated.
     *
     * @param realm The newly associated Realm
     */
    public void setRealm(Realm realm);

    // --------------------------------------------------------- Public Methods


    /**
     * Execute a periodic task, such as reloading, etc. This method will be invoked inside the
     * classloading context of this container. Unexpected throwables will be caught and logged.
     */
    public void backgroundProcess();


    /**
     * Add a new child Container to those associated with this Container, if supported.  Prior to
     * adding this Container to the set of children, the child's <code>setParent()</code> method must
     * be called, with this Container as an argument.  This method may thrown an
     * <code>IllegalArgumentException</code> if this Container chooses not
     * to be attached to the specified Container, in which case it is not added
     *
     * @param child New child Container to be added
     * @throws IllegalArgumentException if this exception is thrown by the <code>setParent()</code>
     * method of the child Container
     * @throws IllegalArgumentException if the new child does not have a name unique from that of
     * existing children of this Container
     * @throws IllegalStateException if this Container does not support child Containers
     */
    public void addChild(Container child);


    /**
     * Add a container event listener to this component.
     *
     * @param listener The listener to add
     */
    public void addContainerListener(ContainerListener listener);


    /**
     * Add a property change listener to this component.
     *
     * @param listener The listener to add
     */
    public void addPropertyChangeListener(PropertyChangeListener listener);


    /**
     * Obtain a child Container by name.
     *
     * @param name Name of the child Container to be retrieved
     * @return The child Container with the given name or <code>null</code> if no such child exists.
     */
    public Container findChild(String name);


    /**
     * Obtain the child Containers associated with this Container.
     *
     * @return An array containing all children of this container. If this Container has no children,
     * a zero-length array is returned.
     */
    public Container[] findChildren();


    /**
     * Obtain the container listeners associated with this Container.
     *
     * @return An array containing the container listeners associated with this Container. If this
     * Container has no registered container listeners, a zero-length array is returned.
     */
    public ContainerListener[] findContainerListeners();


    /**
     * Remove an existing child Container from association with this parent Container.
     *
     * @param child Existing child Container to be removed
     */
    public void removeChild(Container child);


    /**
     * Remove a container event listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removeContainerListener(ContainerListener listener);


    /**
     * Remove a property change listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removePropertyChangeListener(PropertyChangeListener listener);


    /**
     * Notify all container event listeners that a particular event has occurred for this Container.
     * The default implementation performs this notification synchronously using the calling thread.
     *
     * @param type Event type
     * @param data Event data
     */
    public void fireContainerEvent(String type, Object data);


    /**
     * Log a request/response that was destined for this container but has been handled earlier in the
     * processing chain so that the request/response still appears in the correct access logs.
     *
     * @param request Request (associated with the response) to log
     * @param response Response (associated with the request) to log
     * @param time Time taken to process the request/response in milliseconds (use 0 if not known)
     * @param useDefault Flag that indicates that the request/response should be logged in the
     * engine's default access log
     */
    public void logAccess(Request request, Response response, long time, boolean useDefault);


    /**
     * Obtain the AccessLog to use to log a request/response that is destined for this container. This
     * is typically used when the request/response was handled (and rejected) earlier in the
     * processing chain so that the request/response still appears in the correct access logs.
     *
     * @return The AccessLog to use for a request/response destined for this container
     */
    public AccessLog getAccessLog();


    /**
     * Obtain the number of threads available for starting and stopping any children associated with
     * this container. This allows start/stop calls to children to be processed in parallel.
     *
     * @return The currently configured number of threads used to start/stop children associated with
     * this container
     */
    public int getStartStopThreads();


    /**
     * Sets the number of threads available for starting and stopping any children associated with
     * this container. This allows start/stop calls to children to be processed in parallel.
     *
     * @param startStopThreads The new number of threads to be used
     */
    public void setStartStopThreads(int startStopThreads);


    /**
     * Obtain the location of CATALINA_BASE.
     *
     * @return The location of CATALINA_BASE.
     */
    public File getCatalinaBase();


    /**
     * Obtain the location of CATALINA_HOME.
     *
     * @return The location of CATALINA_HOME.
     */
    public File getCatalinaHome();
}
